The Minnesota couple’s Phoenix wedding would be perfect — all the friends and relatives gathered, a lovely hotel, a beautiful bride, love in the air.But the best man, the aptly-named “Lumpy” (Tyler Labine), is out of control — binge drinking, singing along with every song, a sloppy drunk in every sense.“Why don’t you call it a night?” the groom (Justin Long) begs.“You’re cuttin’ off the BEST MAN?”No point. Lumpy carries the party to his room, injures himself, staggers out into the desert in the middle of the night and dies.“On a CACTUS!” It’s “Best Man Down,” but the bride, Kristen (Jess Weixler) is upset — that her honeymoon, “under a palm tree, in a kaftan, sipping Mai Tais,” is ruined. She’s a self-medicating ball of stress, and Lumpy’s bull-in-a-china-shop stampede through her “big night” has stripped all the sympathy from her. She is irked as all get out when she and new hubby Scott (Long), strapped for cash, have to take Lumpy back to Minnesota and get him buried.“He wasn’t your best friend,” she complains. “He was your oldest friend.”But as they try and set up the funeral and tell Lumpy’s circle of law school classmates, friends and employees at the bar where he worked about his death, Scott starts to figure out he didn’t know Lumpy, this true-blue friend, at all.Ramsey (Addison Timlin) is the pretty, 15-year-old outcast in her new, Northern Minnesota high school. She knew Lumpy, and just how she knew him is what the movie is about. She confides in her gay priest (Michael Landes) and tries to keep the peace between her wandering, waitress mother (Frances O’Connor) and mom’s meth-cooking combat vet boyfriend (Evan Jones). We fret about how she will react when she hears Lumpy has died.“He was in a bad place,” those who knew Lumpy tell Scott. Just how bad he is slow to figure out.Long’s unassuming charm is put to good use here, and a brittle Weixler plays off that to great effect.Labine (“Tucker & Dale vs. Evil”) is mostly seen in disarming flashbacks, showing what Lumpy was to those who really knew him. It’s an irritating performance that turns touching.Which is the arc of “Best Man Down” as well. With actors like Shelley Long (mother of the bride) in support, the cute scenes and awkwardly amusing ones tumble by, painting the picture of newlyweds facing their first big fight as they meet one troubled soul after another. Writer-director Ted Koland can be a little obvious. It’s not a deep movie. But everybody, especially Ramsey, is dealing with something. And Timlin (TV’s “Zero Hour”) gives heart to this wonderful, nuanced character. The best man may be down, but Timlin’s Ramsey is the vulnerable, smart and foundering soul who has reasons for missing him that the groom can barely fathom in this sad, surprisingly affecting little comedy.